If you could travel at the speed of light...

[stormgol]

https://en.wikipedia.org/wiki/Gravitational_wave

 

[ATex7239]

Wow! And just think with the massive expanses of the known universe and somehow I’m at the center of it.

 

[jghall00]

No, we measure waves directly. It’s probably both particles and waves, but either way we are directly measuring it. It’s not an effect that’s being measured.

Unless you don’t believe we directly measure light?

The unit of light is a photon. I can build a detector that will measure the intensity of the light, as well as its wavelength. What is the equivalent unit for gravity? Yes, we observe gravitational waves. But again, that's an effect of gravity, not gravity itself. Dark matter and dark energy are conjectures, because we see the gravitational effects, but don't understand the root cause. As I said, we still don't have a theory that adequately explains gravity. Reconciling general relativity and quantum mechanics is an entire branch of physics.

So no, dark matter is not directly observed, but its effects are - and to be honest, the name, dark matter is derived from the fact that there must be a mass, but it doesn’t emit light. This is still a very theoretical construct.

I don’t know what objects you’re talking about passing beyond what horizons, but we can see back to the beginning of the universe by examining the background radiation, and we can see 14 billion years into the past and 14 billion light years distant.

I agree—that's my point. Once objects cross beyond the cosmic horizon we can't see them, but that doesn't mean they are no longer there. There's a difference between being able to see something because our tech has improved, vs it being unobservable because it's light can't reach us. My original statement was that objects are disappearing to a distance beyond which they are not observable. You said we can see 14 billion light years distant, which is incorrect. We can see up to 46 billion light years distant because space has expanded. But beyond that, nothing is observable.

 

[kschachn]

The unit of light is a photon. I can build a detector that will measure the intensity of the light, as well as its wavelength. What is the equivalent unit for gravity? Yes, we observe gravitational waves. But again, that's an effect of gravity, not gravity itself. Dark matter and dark energy are conjectures, because we see the gravitational effects, but don't understand the root cause. As I said, we still don't have a theory that adequately explains gravity. Reconciling general relativity and quantum mechanics is an entire branch of physics.

Oy.

We are dectecting gravity directly. All that other stuff you’re going on about is not refuting what I said.

 

[kschachn]

I agree—that's my point. Once objects cross beyond the cosmic horizon we can't see them, but that doesn't mean they are no longer there. There's a difference between being able to see something because our tech has improved, vs it being unobservable because it's light can't reach us. My original statement was that objects are disappearing to a distance beyond which they are not observable. You said we can see 14 billion light years distant, which is incorrect. We can see up to 46 billion light years distant because space has expanded. But beyond that, nothing is observable.

Objects are not disappearing. In fact the particle horizon is receding with time for all observers.

 

[Pablo]

We simply cannot accelerate to the point of escaping a dog fart. Once detected by the very definition one has not escaped.

 

[walterjay]

And my kids would still be asking........"are we there yet?"

 

[Astro14]

The unit of light is a photon. I can build a detector that will measure the intensity of the light, as well as its wavelength. What is the equivalent unit for gravity? Yes, we observe gravitational waves. But again, that's an effect of gravity, not gravity itself. Dark matter and dark energy are conjectures, because we see the gravitational effects, but don't understand the root cause. As I said, we still don't have a theory that adequately explains gravity. Reconciling general relativity and quantum mechanics is an entire branch of physics.

I agree—that's my point. Once objects cross beyond the cosmic horizon we can't see them, but that doesn't mean they are no longer there. There's a difference between being able to see something because our tech has improved, vs it being unobservable because it's light can't reach us. My original statement was that objects are disappearing to a distance beyond which they are not observable. You said we can see 14 billion light years distant, which is incorrect. We can see up to 46 billion light years distant because space has expanded. But beyond that, nothing is observable.

I don’t buy that - it’s a semantic argument that we can see 46 GLY distant, because that is how far the object is now.

The objects that we can see are about 13.5 GLY distant because that’s how far the photons have traveled. We are looking back in time, to when the universe was much smaller, but we aren’t looking farther just because the object has become more distant through expansion.

The 46 GLY argument is like saying, “I saw that ship a mile offshore”. But after it has sailed 3 more miles, you say, “Now I can see 4 miles”.

Well, no, you can still only see the mile that you first saw it, despite what it may have done since the photons began their journey.

And object that are more distant will never be visible because the light would have had to begin the journey before the Big Bang, and that simply is impossible. The more distant you look, the farther back you are seeing, and there is an ultimate limit to how far back you can see - the age of the universe bounds that set of observations.

 

[PandaBear]

My money is betting that some of the equations and math we use today will not work the same at the larger scale like billion light years distance. We human tends to assume a lot of things staying the same and linear in that much of a scale away.

For now, "if I could travel at the speed of light", my time would stop completely.

 

[k1xv]

I traveled at the speed of light when I moved from New Jersey to Vermont.

 

[Pew]

Wow! And just think with the massive expanses of the known universe and somehow I’m at the center of it.

Oh no stop, my steak is too juicy and my lobster is too buttery.

 

[Pablo]

If you go fast enough Schrodingers Cat becomes Pablo’s Dog

 

[Analog-1]

Well riddle me this. If the universe is constantly expanding and everything is moving away from one another than why is Andromeda going to collide with our Milkyway galaxy ?

 

[4WD]

If you go fast enough Schrodingers Cat becomes Pablo’s Dog

Especially around dinner time in Korea

 

[StarCaller]

Well riddle me this. If the universe is constantly expanding and everything is moving away from one another than why is Andromeda going to collide with our Milkyway galaxy ?

Expansion is not like raisins on a loaf of bread being physically pushed apart by some force /
It’s more that space itself stretches on the largest scales; however, local gravity can completely overpower that stretching when objects are relatively close together /

 

[HemiBenny]

It's all fun and games until you bump into Klingons, Romulans, and the Borg.

All kidding aside, I can't believe that we're alone in this universe.

 

[KrisZ]

It's a projection/simulation running on an equivalent of an Intel 486 processor with a whopping 8MB of ram. So it obviously cannot compute everything everywhere at the same time. It simulates everything properly in our solar system and the further away we look, the more things start to break down, all because the intern was lazy with their code and figured we would never be able to see that far away.

Well, we proved the intern wrong. But I guess the intern has the last laugh because even with the speed of light, we aren't going anywhere beyond our solar system, ever.

 

[JeffKeryk]

Youz guys are awesome.

I don’t know what objects you’re talking about passing beyond what horizons, but we can see back to the beginning of the universe by examining the background radiation, and we can see 14 billion years into the past and 14 billion light years distant. There’s not a lot of matter that is “passing the horizon” except, perhaps, for the accretion discs around black holes, where matter crosses the event horizon, and which represents a really small amount of the universe, and which has negligible affect on our ability to understand what we do see.

I took it to mean the event horizon of a black hole. Light cannot escape its gravitational pull; it cannot be seen from outside the black hole.
Right?

 

[KrisZ]

Youz guys are awesome.

I took it to mean the event horizon of a black hole. Light cannot escape its gravitational pull; it cannot be seen from outside the black hole.
Right?

No, there is a universe edge or cosmic horizon or particle horizon as well, beyond which we cannot detect anything.

 

[Pablo]

Especially around dinner time in Korea

Enough loaves and “meat” to feed thousands.