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> My renowned astrophysics professor taught us how the universe seemed to be expanding, but never bothered to explain what it was expanding into (still waiting

> My renowned astrophysics professor taught us how the universe seemed to be expanding, but never bothered to explain what it was expanding into (still waiting for someone to demystify that one). Wow... and this person went to Harvard??

foo101 8y ago
I want to know the answer too. I always thought the universe is expanding to a larger universe. I never thought that it could be expanding to something else.
- fvdessen 8y ago
  the universe doesn’t expand into something bigger. It’s like multiplying the set of the real numbers by two, the set doesn’t become bigger and its boundaries do not change.
  - foo101 8y ago
    I think you or someone understands this subject should write a detailed comment in this thread that explains this to software folks like us. I appreciate the help.
- Moodles 8y ago
  I think it’s like the universe being a balloon (infinite or not) and inflating it. The space between any two points on the balloon increases over time. And at the Big Bang the space was basically 0.
- olavk 8y ago
  Think of it another way: All matter in the universe is getting smaller. But the universe have the same size, so distances between everything increase.
- mockingbirdy 8y ago
  There's no notion of spacetime outside the universe. The spacetime is the universe. Two assumptions: a) the universe is infinite. In this case it doesn't expand into anything, the things inside of it just stretch apart. b) the universe is finite. In this case it expands into something, but because we're trapped inside spacetime, we can't answer this scientifically. The wording "expanding" adds more confusion than it helps. See [1] for the discussion about this topic. [1]: http://curious.astro.cornell.edu/ask-a-question/104-the-universe/cosmology-and-the-big-bang/expansion-of-the-universe/623-what-is-the-universe-expanding-into-intermediate http://curious.astro.cornell.edu/ask-a-question/104-the-univ...
fipple 8y ago
What’s the answer? Curious.
- WilliamEdward 8y ago
  It's not expanding, separate points are growing further apart. Any metaphor you hear about a balloon or fabric or things like that is an overly simplified version of complicated mathematical models of the universe.
  - mcny 8y ago
    Are electrons getting larger? Are atoms getting larger?
    - WilliamEdward 8y ago
      Long story short, no and that's because forces are only applicable in certain situations and not others, and in this case gravity, electromagnetism, and similar subatomic forces are binding the atoms we know and preventing them from "expanding". I'm not an expert and this is just my simplified version of a simplified version. Here's more to read about it: https://www.quora.com/Astrophysics-If-the-universe-is-expanding-why-arent-we-expanding https://www.quora.com/Astrophysics-If-the-universe-is-expand... https://medium.com/starts-with-a-bang/ask-ethan-if-the-universe-is-expanding-why-arent-we-71b46b5e9974 https://medium.com/starts-with-a-bang/ask-ethan-if-the-unive...
LoSboccacc 8y ago
I doubt a renowned professor would use expanding instead of inflating. likely the student got stuck on the balloon metaphor.
ur-whale 8y ago
Explaining what is/was "around" the big-bang was never done properly in most physics courses I've taken, and for a good reason: you need to understand the notion of local space metric before you can get that - as the theory currently stands - there is basically nothing outside of the expanding universe.
- WilliamEdward 8y ago
  There are some things humans will simply never be able to come into contact with or fully comprehend. Such things include the 4th dimension, the concept of infinity, and the concept of nothingness. The universe and what lies outside of it, unfortunately involves all of these concepts, so while there may or not be nothing beyond the universe, because we cannot measure this or engage with this, it is only effectively nothing and not literally nothing.
  - ur-whale 8y ago
    Is the universe infinite? Debatable.

foo101 8y ago

I want to know the answer too. I always thought the universe is expanding to a larger universe. I never thought that it could be expanding to something else.

fvdessen 8y ago
the universe doesn’t expand into something bigger. It’s like multiplying the set of the real numbers by two, the set doesn’t become bigger and its boundaries do not change.
- foo101 8y ago
  I think you or someone understands this subject should write a detailed comment in this thread that explains this to software folks like us. I appreciate the help.
Moodles 8y ago
I think it’s like the universe being a balloon (infinite or not) and inflating it. The space between any two points on the balloon increases over time. And at the Big Bang the space was basically 0.
olavk 8y ago
Think of it another way: All matter in the universe is getting smaller. But the universe have the same size, so distances between everything increase.
mockingbirdy 8y ago
There's no notion of spacetime outside the universe. The spacetime is the universe. Two assumptions: a) the universe is infinite. In this case it doesn't expand into anything, the things inside of it just stretch apart. b) the universe is finite. In this case it expands into something, but because we're trapped inside spacetime, we can't answer this scientifically. The wording "expanding" adds more confusion than it helps. See [1] for the discussion about this topic. [1]: http://curious.astro.cornell.edu/ask-a-question/104-the-universe/cosmology-and-the-big-bang/expansion-of-the-universe/623-what-is-the-universe-expanding-into-intermediate http://curious.astro.cornell.edu/ask-a-question/104-the-univ...

fipple 8y ago

What’s the answer? Curious.

WilliamEdward 8y ago
It's not expanding, separate points are growing further apart. Any metaphor you hear about a balloon or fabric or things like that is an overly simplified version of complicated mathematical models of the universe.
- mcny 8y ago
  Are electrons getting larger? Are atoms getting larger?
  - WilliamEdward 8y ago
    Long story short, no and that's because forces are only applicable in certain situations and not others, and in this case gravity, electromagnetism, and similar subatomic forces are binding the atoms we know and preventing them from "expanding". I'm not an expert and this is just my simplified version of a simplified version. Here's more to read about it: https://www.quora.com/Astrophysics-If-the-universe-is-expanding-why-arent-we-expanding https://www.quora.com/Astrophysics-If-the-universe-is-expand... https://medium.com/starts-with-a-bang/ask-ethan-if-the-universe-is-expanding-why-arent-we-71b46b5e9974 https://medium.com/starts-with-a-bang/ask-ethan-if-the-unive...

LoSboccacc 8y ago

I doubt a renowned professor would use expanding instead of inflating. likely the student got stuck on the balloon metaphor.

ur-whale 8y ago

Explaining what is/was "around" the big-bang was never done properly in most physics courses I've taken, and for a good reason: you need to understand the notion of local space metric before you can get that - as the theory currently stands - there is basically nothing outside of the expanding universe.

WilliamEdward 8y ago
There are some things humans will simply never be able to come into contact with or fully comprehend. Such things include the 4th dimension, the concept of infinity, and the concept of nothingness. The universe and what lies outside of it, unfortunately involves all of these concepts, so while there may or not be nothing beyond the universe, because we cannot measure this or engage with this, it is only effectively nothing and not literally nothing.
- ur-whale 8y ago
  Is the universe infinite? Debatable.