4 ms·

You are the oldest thing in the universe you can observe. Even the person next to you, as you observe her or him, is younger, because the speed of light is fini

You are the oldest thing in the universe you can observe. Even the person next to you, as you observe her or him, is younger, because the speed of light is finite. In this respect, you are the centre of your universe. But objectively speaking, there is no centre.

p1esk 4y ago
This doesn’t make any sense
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- tromp 4y ago
  When you see someone standing 3m away from you, the light took 10 nanoseconds to reach your eye, so you see them as they were a very short time ago. Of course, they're only younger when measuring their age not from their birth but from the big bang.
- jpollock 4y ago
  I find it useful to think of photons as vector clocks: https://en.wikipedia.org/wiki/Vector_clock https://en.wikipedia.org/wiki/Vector_clock Take a photon starting from your chest and give it t1. * Assume that the speed of light is symmetrical. * When the photon hits the next person's eyes, it is t1 + distance/speed of light. Meaning, the photon is "from the past". Since all photons arriving are from the past, the photons travelling the shortest distance are the newest (representing the largest timestamp). So, the thing with the largest observable timestamp is yourself.
  - p1esk 4y ago
    We are not talking about the age of photons. We are talking about the age of the thing that emits/reflects photons. The confusion arose because the OP said "you are the oldest thing in the universe you can observe". They should have said "you are the most recent thing in the universe you can observe".
    - ncmncm 4y ago
      Strangely enough, everything that emitted a photon is at least as old as that photon.
- brianpan 4y ago
  It's similar to how every sound you hear is of an event in the near past. Every thunderclap is caused by a past and distant lightning event. As a child, we'd see lightning and then count seconds waiting to hear the thunder (sound travels slower and takes longer to arrive than the light- about 2 seconds per mile). If you're hearing thunder now, in a way, you're hearing an event in the past. The farther the thunder traveled, the farther into the past you are experiencing. Across the expanse of space, you are not just hearing, but seeing into the past. The farther the light traveled, the farther into the past you are experiencing now.
  - p1esk 4y ago
    Yeah, so I’m older than the lightning. Am I also older than the sun? By this logic, I'm the newest thing in the universe, because it takes the shortest time for me to observe myself.
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    - brianpan 4y ago
      I re-read the parent comment and I see why you're confused. It was awkwardly worded. "Older" and "younger" are confusing ways to put it. The fact is, simultaneous observations don't necessarily mean simultaneous events. If you hear 2 people shouting at the same time, but one person is very far away and one person is near, you can assume the person farther away actually shouted first. The reason this happens is the different delay across different distances. The distances have to be much greater to notice the difference with light compared to sound. But compared to the expanse of the universe, light actually travels quite slowly. If the sun disappeared, we wouldn't see it disappear on Earth for 8 minutes (that's how long it takes light to reach Earth). Essentially, we are seeing the Sun as it was 8 minutes in the past. The effect is even greater outside our solar system and even greater beyond our galaxy. We see stars and galaxies as they were, not just minutes but years and years in the past. Some stars that we see now have certainly already reached the end of their life, exploded into a supernova and collapsed. We just haven't seen it yet. The light from those events haven't reached us yet. Everything we see is of something as it was in the past. Even though we are seeing all the stars and galaxies simultaneously, the farther away it is, the farther into the past we are observing.
mrits 4y ago
So I'm older than my grandparents?
- thatwasunusual 4y ago
  From your perspective, you're the oldest in the whole universe, AND you're the center of the universe. Congratulations! :)
  - varajelle 4y ago
    No. Not according to the classical definition of age which is the time since birth. I was born a few decade ago. My grandparents are decades older then me. The earth in millions of year older than me. And the galaxies billions of lightyears away are still billions of year older than me. Maybe the Milkyway is older than the other galaxies we observe, assuming they were all born at the same time.
    - thatwasunusual 4y ago
      > No. Not according to the classical definition of age which is the time since birth. We're not talking about the classical definition of age.
- Taniwha 4y ago
  oldest since the big bang, not oldest since you were created
nwallin 4y ago
> You are the oldest thing in the universe you can observe. The moon is older than we are, due to gravitational time dilation. So is Mars. Even if you account for the time it takes for light to travel to here from there.
Archelaos 4y ago
Reading the responses, I think I need to explain a little more fully what I meant. My remark was intented as an explanation of one of the parents' statement: "distant means younger" when observing astronomical objects. We are not talking here about the age of the object per se (how old is the star I see, etc.), but about the age of the observation (how long ago did that happen, what I see just now). Every look into the sky is a look into the past. But also every look around you is a look into the past. With "the oldest thing in the universe", I did mean the particles that form you (not you as a specific formation of such particles). If we say that everything of the universe started at the same time, then the atoms closest to you are the oldest things in the universe you can observe. Objectively, of course, every particle has the same age, even though it might be beyond the event horizon and never be observable. (I am simplifying somewhat here, leaving the spontanous coming and going of particles in the vaccum out of the picture.)

p1esk 4y ago

This doesn’t make any sense

deleted 4y ago
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deleted 4y ago
[deleted]
tromp 4y ago
When you see someone standing 3m away from you, the light took 10 nanoseconds to reach your eye, so you see them as they were a very short time ago. Of course, they're only younger when measuring their age not from their birth but from the big bang.
jpollock 4y ago
I find it useful to think of photons as vector clocks: https://en.wikipedia.org/wiki/Vector_clock https://en.wikipedia.org/wiki/Vector_clock Take a photon starting from your chest and give it t1. * Assume that the speed of light is symmetrical. * When the photon hits the next person's eyes, it is t1 + distance/speed of light. Meaning, the photon is "from the past". Since all photons arriving are from the past, the photons travelling the shortest distance are the newest (representing the largest timestamp). So, the thing with the largest observable timestamp is yourself.
- p1esk 4y ago
  We are not talking about the age of photons. We are talking about the age of the thing that emits/reflects photons. The confusion arose because the OP said "you are the oldest thing in the universe you can observe". They should have said "you are the most recent thing in the universe you can observe".
  - ncmncm 4y ago
    Strangely enough, everything that emitted a photon is at least as old as that photon.
brianpan 4y ago
It's similar to how every sound you hear is of an event in the near past. Every thunderclap is caused by a past and distant lightning event. As a child, we'd see lightning and then count seconds waiting to hear the thunder (sound travels slower and takes longer to arrive than the light- about 2 seconds per mile). If you're hearing thunder now, in a way, you're hearing an event in the past. The farther the thunder traveled, the farther into the past you are experiencing. Across the expanse of space, you are not just hearing, but seeing into the past. The farther the light traveled, the farther into the past you are experiencing now.
- p1esk 4y ago
  Yeah, so I’m older than the lightning. Am I also older than the sun? By this logic, I'm the newest thing in the universe, because it takes the shortest time for me to observe myself.
  - deleted 4y ago
    [deleted]
  - deleted 4y ago
    [deleted]
  - brianpan 4y ago
    I re-read the parent comment and I see why you're confused. It was awkwardly worded. "Older" and "younger" are confusing ways to put it. The fact is, simultaneous observations don't necessarily mean simultaneous events. If you hear 2 people shouting at the same time, but one person is very far away and one person is near, you can assume the person farther away actually shouted first. The reason this happens is the different delay across different distances. The distances have to be much greater to notice the difference with light compared to sound. But compared to the expanse of the universe, light actually travels quite slowly. If the sun disappeared, we wouldn't see it disappear on Earth for 8 minutes (that's how long it takes light to reach Earth). Essentially, we are seeing the Sun as it was 8 minutes in the past. The effect is even greater outside our solar system and even greater beyond our galaxy. We see stars and galaxies as they were, not just minutes but years and years in the past. Some stars that we see now have certainly already reached the end of their life, exploded into a supernova and collapsed. We just haven't seen it yet. The light from those events haven't reached us yet. Everything we see is of something as it was in the past. Even though we are seeing all the stars and galaxies simultaneously, the farther away it is, the farther into the past we are observing.

mrits 4y ago

So I'm older than my grandparents?

thatwasunusual 4y ago
From your perspective, you're the oldest in the whole universe, AND you're the center of the universe. Congratulations! :)
- varajelle 4y ago
  No. Not according to the classical definition of age which is the time since birth. I was born a few decade ago. My grandparents are decades older then me. The earth in millions of year older than me. And the galaxies billions of lightyears away are still billions of year older than me. Maybe the Milkyway is older than the other galaxies we observe, assuming they were all born at the same time.
  - thatwasunusual 4y ago
    > No. Not according to the classical definition of age which is the time since birth. We're not talking about the classical definition of age.
Taniwha 4y ago
oldest since the big bang, not oldest since you were created

nwallin 4y ago

> You are the oldest thing in the universe you can observe. The moon is older than we are, due to gravitational time dilation. So is Mars. Even if you account for the time it takes for light to travel to here from there.

Archelaos 4y ago

Reading the responses, I think I need to explain a little more fully what I meant. My remark was intented as an explanation of one of the parents' statement: "distant means younger" when observing astronomical objects. We are not talking here about the age of the object per se (how old is the star I see, etc.), but about the age of the observation (how long ago did that happen, what I see just now). Every look into the sky is a look into the past. But also every look around you is a look into the past. With "the oldest thing in the universe", I did mean the particles that form you (not you as a specific formation of such particles). If we say that everything of the universe started at the same time, then the atoms closest to you are the oldest things in the universe you can observe. Objectively, of course, every particle has the same age, even though it might be beyond the event horizon and never be observable. (I am simplifying somewhat here, leaving the spontanous coming and going of particles in the vaccum out of the picture.)