6 ms·

It's crazy how violent these events are. I remember reading about one of the first where an estimated 5 Solar masses were converted into energy in about a secon

by cletus 5y ago

It's crazy how violent these events are. I remember reading about one of the first where an estimated 5 Solar masses were converted into energy in about a second, which is why it distorted space a billion light years away. I have some questions. 1. What if you were 1 light year from such an event? What would you experience? What about 100 light years? 2. What does warping spacetime really mean? I know this happens around a black hole. But what would the macro effects of this be? 3. So the universe is expanding. Does that mean more "space" is being made? If so, how? Out of what?

diegoperini 5y ago
2. One macro effect would be (assuming the observer is at a safe distance) unexpected tidal waves in the oceans seeming to appear from nowhere right after the merger.
NegativeLatency 5y ago
Possibly your atoms, and probably your molecules would be ripped apart by the gamma rays and other particles emitted before a shockwave hit?
- AnimalMuppet 5y ago
  Before? Gravitational waves travel at the speed of light too... (Or are you saying that the gamma rays are emitted earlier in the merger process than the gravitational waves?)
  - goldenkey 5y ago
    A better way to think of the speed of light is as the stiffness of spacetime. This allows for you to intuit what warping effects do to the trajectory of light and gravity.
ben_w 5y ago
Frustratingly, when I tried to ask on Physics Stack Exchange if you could hear a gravitational wave and if so how powerful it would have to be, I managed to simultaneously have the question closed as a duplicate with a link to someone saying “yes” without saying how powerful, and find the top answer on my question was “no”. https://physics.stackexchange.com/questions/560833/could-a-human-even-in-principle-hear-a-gravitational-wave-if-so-how-powerful https://physics.stackexchange.com/questions/560833/could-a-h...
- Thorondor 5y ago
  Hi Ben, as the person who initially flagged your question as a duplicate, I'm sorry. I can see why this was frustrating. I'll try to provide a more detailed answer here. According to a 1948 paper by Bekesy [0], a human ear can detect sounds through several mechanisms. In a gravitational wave, since the whole head would vibrate, sound would reach the ear by bone conduction through the skull. Fortunately, this also happens to be the most sensitive mechanism. The smallest vibration amplitude detectable by bone conduction is about 4 x 10^-9 cm at around 3 kHz. If a typical skull is about 17.5 cm from front to back, that gives a minimum detectable wave amplitude h (the fractional expansion and contraction of spacetime) of about 2 x 10^-10. The frequency of the gravitational waves produced in a collision between a neutron star and a small black hole turns out to be pretty close to an optimal match for the human ear. To estimate the amplitude, the first black hole collision detected at LIGO produced a strain of about 10^-21 at a distance of 410 Mpc. (The events in the article were smaller, but within the same order of magnitude.) Thus, since the amplitude scales as 1/r, the gravitational waves from the collision in the article would have been theoretically audible at a distance of about 400 AU or 40 billion miles. Alas, attempting to test this calculation experimentally would incur certain practical difficulties. Notably, you would be vaporized by gamma radiation from the collision several seconds before the gravitational waves became audible. [0]: https://asa.scitation.org/doi/10.1121/1.1906433 https://asa.scitation.org/doi/10.1121/1.1906433
  - java-man 5y ago
    why not post this answer to physics.stackexchange.com?
    - Thorondor 5y ago
      The question is currently closed, so I can't post a new answer. I voted to reopen it, and I've edited the title to focus on the aspect of the question that is not adequately answered by the duplicate.
      - R0b0t1 5y ago
immmmmm 5y ago
i'm a former physicist but yeah, a few stellar masses worth of energy is beyond (my) imagination 1. always wondered the same. i'd suspect that for most astronomical BH you would first need to worry of X/gamma rays. you could possibly hear a loud chirp since it is audio frequency. 2. the warping of space time here on earth is actually mostly a warping of time, which is even weirder. i means that the time at your feet is flowing slower that where you're head is. about one second on your entire life. that's actually WHY you feel earth gravity. 3. yes, more space is created out of nothing! because there's a vacuum energy density that inflate the local patch of universe. funnily why all of the above is hard to understand for our human brains, it all makes sense in the mathematics.. i highly recommend the YT channel PBS Space Time for more explanations
- macspoofing 5y ago
  >yes, more space is created out of nothing! because there's a vacuum energy density that inflate the local patch of universe. I don't think you can say that with that kind of certainty. We don't have a theory of quantum gravity, we don't know what dark matter is, and we don't know what 'dark energy' is, so we don't actually know what is driving the expansion of the universe, so saying that 'space is created out of nothing' is too strong. Even something like the theory of cosmological inflation, which has some explanatory power, hasn't been experimentally verified, but rather tuned to match the observations. It's something I've noticed in a lot of communicators of science (whether they have a background in science or not). They tend use terms that overstate our actual knowledge in some specific area of science.
  - Iwan-Zotow 5y ago
    > I don't think you can say that with that kind of certainty. well, any classic (in SM sense) QFT will produce positive vacuum energy density which translates into negative pressure. P = -E
  - immmmmm 5y ago
    you're absolutely correct, i was referring to models based on classical GR + QFT (standard cosmology + standard model). ofc those are wrong but yield the most accurate predictions any models has ever yielded. i'm almost certain (no proof tho) that space time itself is just an illusion (and that there is only "information "). in other term i know i know nothing (but still is able to give predictions up 10^-32 s after big bang)
bmitc 5y ago
I don't have answers for you, but you might be interested in the book Black Holes and Time Warps: Einstein's Outrageous Legacy by Kip Thorne. https://www.amazon.com/Black-Holes-Time-Warps-Commonwealth/dp/0393312763 https://www.amazon.com/Black-Holes-Time-Warps-Commonwealth/d...
tzs 5y ago
I'm not sure if answers to those specific questions are there, but in general PBS Space Time deals with that kind of thing (and a lot more). Here's their YouTube channel [1] and here is their page at PBS.org [2]. It's also available via the PBS app on many streaming devices and smart TVs. Most of their videos are in the 8-13 minute length, and they do a pretty good job at the start of each linking back to earlier episodes that cover prior material that the current video builds on, so if you see a video whose title/topic seems interesting it is fine to start their first. [1] https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g [2] https://www.pbs.org/show/pbs-space-time/ https://www.pbs.org/show/pbs-space-time/
drran 5y ago
1. 5 solar masses is 1x10^34 g. 1 g of mass is roughly 0.9x10^14 J (mc^2). So, roughly 1x10^48 J. 1 ly is roughly 1x10^16 m. Surface area of a sphere with r=1 ly, is 4πr^2 = 4π x 10^32 m^2 or roughly 1x10^33, so each m^2 of surface will receive 1x10^48/1x10^33 = 10^15 Watt, or about 10^12 x brighter than our Sun on Earth in sunny day, but for 1 second only. 2. Spacetime is 4d array: [x,y,z;t]. Warping of spacetime means that a scientist applies a mathematical formula to the array directly, like shader in OpenGL. It has no physical meaning. It just a quick way to simulate unknown physical process, to make a prediction. 3. No, it doesn't. Our local group of galaxies is expanding, but this is a coincidence. Actually, we are falling into a black hole. Nearest big black hole is in the center of our galaxy, then Great Attractor, then Shapley Attractor.
- hypertele-Xii 5y ago
  > about 100x brighter than our Sun on Earth in sunny day, but for 1 second only. Sounds hot. Flash burn everything not made of stone. Land life wouldn't survive?
  - drran 5y ago
    I made a mistake in the calculation (10^34 x 10^14 is 10^48, not 10^38), so it's 10^12 brighter. Nobody will survive on the lit surface of a planet.
    - phasetransition 5y ago
      So 1e6 light year radius to match the solar irradiance from purely inverse square losses? Wow.
    - x3n0ph3n3 5y ago
      And it would likely ignite the atmosphere, which would travel at the speed of sound to the "dark" side of the planet, yes?
  - ben_w 5y ago
    It would have that effect if the energy was in the form of photons, but it is gravity waves. If you release 5 solar masses of energy in one second, electromagnetically and with the same spectrum as the sun, half way between the Milky Way and Andromeda, every star in both galaxies would see it only a little dimmer as Sol appears on Mars. https://www.wolframalpha.com/input/?i=%28%28%285+solar+mass%29*c%5E2%29%2F%281+second%29%29+%2F+%284π%281.287e6+ly%29%5E2%29 https://www.wolframalpha.com/input/?i=%28%28%285+solar+mass%...

by cletus 5y ago

diegoperini 5y ago

2. One macro effect would be (assuming the observer is at a safe distance) unexpected tidal waves in the oceans seeming to appear from nowhere right after the merger.

NegativeLatency 5y ago

Possibly your atoms, and probably your molecules would be ripped apart by the gamma rays and other particles emitted before a shockwave hit?

AnimalMuppet 5y ago
Before? Gravitational waves travel at the speed of light too... (Or are you saying that the gamma rays are emitted earlier in the merger process than the gravitational waves?)
- goldenkey 5y ago
  A better way to think of the speed of light is as the stiffness of spacetime. This allows for you to intuit what warping effects do to the trajectory of light and gravity.

ben_w 5y ago

Frustratingly, when I tried to ask on Physics Stack Exchange if you could hear a gravitational wave and if so how powerful it would have to be, I managed to simultaneously have the question closed as a duplicate with a link to someone saying “yes” without saying how powerful, and find the top answer on my question was “no”. https://physics.stackexchange.com/questions/560833/could-a-human-even-in-principle-hear-a-gravitational-wave-if-so-how-powerful https://physics.stackexchange.com/questions/560833/could-a-h...

Thorondor 5y ago
Hi Ben, as the person who initially flagged your question as a duplicate, I'm sorry. I can see why this was frustrating. I'll try to provide a more detailed answer here. According to a 1948 paper by Bekesy [0], a human ear can detect sounds through several mechanisms. In a gravitational wave, since the whole head would vibrate, sound would reach the ear by bone conduction through the skull. Fortunately, this also happens to be the most sensitive mechanism. The smallest vibration amplitude detectable by bone conduction is about 4 x 10^-9 cm at around 3 kHz. If a typical skull is about 17.5 cm from front to back, that gives a minimum detectable wave amplitude h (the fractional expansion and contraction of spacetime) of about 2 x 10^-10. The frequency of the gravitational waves produced in a collision between a neutron star and a small black hole turns out to be pretty close to an optimal match for the human ear. To estimate the amplitude, the first black hole collision detected at LIGO produced a strain of about 10^-21 at a distance of 410 Mpc. (The events in the article were smaller, but within the same order of magnitude.) Thus, since the amplitude scales as 1/r, the gravitational waves from the collision in the article would have been theoretically audible at a distance of about 400 AU or 40 billion miles. Alas, attempting to test this calculation experimentally would incur certain practical difficulties. Notably, you would be vaporized by gamma radiation from the collision several seconds before the gravitational waves became audible. [0]: https://asa.scitation.org/doi/10.1121/1.1906433 https://asa.scitation.org/doi/10.1121/1.1906433
- java-man 5y ago
  why not post this answer to physics.stackexchange.com?
  - Thorondor 5y ago
    The question is currently closed, so I can't post a new answer. I voted to reopen it, and I've edited the title to focus on the aspect of the question that is not adequately answered by the duplicate.
    - R0b0t1 5y ago

immmmmm 5y ago

i'm a former physicist but yeah, a few stellar masses worth of energy is beyond (my) imagination 1. always wondered the same. i'd suspect that for most astronomical BH you would first need to worry of X/gamma rays. you could possibly hear a loud chirp since it is audio frequency. 2. the warping of space time here on earth is actually mostly a warping of time, which is even weirder. i means that the time at your feet is flowing slower that where you're head is. about one second on your entire life. that's actually WHY you feel earth gravity. 3. yes, more space is created out of nothing! because there's a vacuum energy density that inflate the local patch of universe. funnily why all of the above is hard to understand for our human brains, it all makes sense in the mathematics.. i highly recommend the YT channel PBS Space Time for more explanations

macspoofing 5y ago
>yes, more space is created out of nothing! because there's a vacuum energy density that inflate the local patch of universe. I don't think you can say that with that kind of certainty. We don't have a theory of quantum gravity, we don't know what dark matter is, and we don't know what 'dark energy' is, so we don't actually know what is driving the expansion of the universe, so saying that 'space is created out of nothing' is too strong. Even something like the theory of cosmological inflation, which has some explanatory power, hasn't been experimentally verified, but rather tuned to match the observations. It's something I've noticed in a lot of communicators of science (whether they have a background in science or not). They tend use terms that overstate our actual knowledge in some specific area of science.
- Iwan-Zotow 5y ago
  > I don't think you can say that with that kind of certainty. well, any classic (in SM sense) QFT will produce positive vacuum energy density which translates into negative pressure. P = -E
- immmmmm 5y ago
  you're absolutely correct, i was referring to models based on classical GR + QFT (standard cosmology + standard model). ofc those are wrong but yield the most accurate predictions any models has ever yielded. i'm almost certain (no proof tho) that space time itself is just an illusion (and that there is only "information "). in other term i know i know nothing (but still is able to give predictions up 10^-32 s after big bang)

bmitc 5y ago

I don't have answers for you, but you might be interested in the book Black Holes and Time Warps: Einstein's Outrageous Legacy by Kip Thorne. https://www.amazon.com/Black-Holes-Time-Warps-Commonwealth/dp/0393312763 https://www.amazon.com/Black-Holes-Time-Warps-Commonwealth/d...

tzs 5y ago

I'm not sure if answers to those specific questions are there, but in general PBS Space Time deals with that kind of thing (and a lot more). Here's their YouTube channel [1] and here is their page at PBS.org [2]. It's also available via the PBS app on many streaming devices and smart TVs. Most of their videos are in the 8-13 minute length, and they do a pretty good job at the start of each linking back to earlier episodes that cover prior material that the current video builds on, so if you see a video whose title/topic seems interesting it is fine to start their first. [1] https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g https://www.youtube.com/channel/UC7_gcs09iThXybpVgjHZ_7g [2] https://www.pbs.org/show/pbs-space-time/ https://www.pbs.org/show/pbs-space-time/

drran 5y ago

1. 5 solar masses is 1x10^34 g. 1 g of mass is roughly 0.9x10^14 J (mc^2). So, roughly 1x10^48 J. 1 ly is roughly 1x10^16 m. Surface area of a sphere with r=1 ly, is 4πr^2 = 4π x 10^32 m^2 or roughly 1x10^33, so each m^2 of surface will receive 1x10^48/1x10^33 = 10^15 Watt, or about 10^12 x brighter than our Sun on Earth in sunny day, but for 1 second only. 2. Spacetime is 4d array: [x,y,z;t]. Warping of spacetime means that a scientist applies a mathematical formula to the array directly, like shader in OpenGL. It has no physical meaning. It just a quick way to simulate unknown physical process, to make a prediction. 3. No, it doesn't. Our local group of galaxies is expanding, but this is a coincidence. Actually, we are falling into a black hole. Nearest big black hole is in the center of our galaxy, then Great Attractor, then Shapley Attractor.

hypertele-Xii 5y ago
> about 100x brighter than our Sun on Earth in sunny day, but for 1 second only. Sounds hot. Flash burn everything not made of stone. Land life wouldn't survive?
- drran 5y ago
  I made a mistake in the calculation (10^34 x 10^14 is 10^48, not 10^38), so it's 10^12 brighter. Nobody will survive on the lit surface of a planet.
  - phasetransition 5y ago
    So 1e6 light year radius to match the solar irradiance from purely inverse square losses? Wow.
  - x3n0ph3n3 5y ago
    And it would likely ignite the atmosphere, which would travel at the speed of sound to the "dark" side of the planet, yes?
- ben_w 5y ago
  It would have that effect if the energy was in the form of photons, but it is gravity waves. If you release 5 solar masses of energy in one second, electromagnetically and with the same spectrum as the sun, half way between the Milky Way and Andromeda, every star in both galaxies would see it only a little dimmer as Sol appears on Mars. https://www.wolframalpha.com/input/?i=%28%28%285+solar+mass%29*c%5E2%29%2F%281+second%29%29+%2F+%284π%281.287e6+ly%29%5E2%29 https://www.wolframalpha.com/input/?i=%28%28%285+solar+mass%...