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Yes. They're right there. See them? Right over there.
Or maybe like Schrodinger's cat, your car keys both exist and don't exist at the same time. You'll only know if they still exist if they can be found.
I am confused. Schrodinger's cat exists. The question is whether it's dead or alive and it could be both dead and alive. So how could it relate to where is the key. They are not even similar. One question is where, the other is state of alive or dead.
I received a PM about "why our Universe makes it look like we're in the center". We are in the center of the Universe as relative to us. What does that mean and why is that though? We can see 13.7 billion light years away from us in *every* direction. That's because the big bang occurred 13.7 billion light years ago. That doesnt mean the Universes edge is 13.7 billion light years away -- it means that light has only had 13.7 billion light years to travel. In 300 million years, we'll be able to see 14 billion light years away. Its our cosmic horizon. That horizon increases 1 light year per year! Lets say you did instantly transmit yourself 13.7 billion light years away from Earth. Your NEW cosmic horizon, relative to your new location, means you are still in the center and everything around you goes out as far as 13.7 billion light years. So to anyone, you are the center of your own Universe. But it is not the center of all that exists, its just the limit on how long light can travel to you based on the age of the Universe.
Ben
What do you mean by we are seeing 13.7 billion light year away from us ? Do you forget to factor in the expansion of the universe? If the universe was expanding then what you are seeing in any direction won't be 13.7 billion light years away but actually 13.7 billions light years + some factoring for expansion. That's the observable universe and it's actually closer to 46 billion light years.
I am confused. Schrodinger's cat exists. The question is whether it's dead or alive and it could be both dead and alive. So how could it relate to where is the key. They are not even similar. One question is where, the other is state of alive or dead.
Post of the day! But I need to drink more beer to understand it.
Will it ever be possible to build a Hubble like telescope that can zoom far enough to a planet that's light years away and make out things on the surface given there's no cloud cover or a thick atmosphere?
Assuming that's possible, how long would that thing be?
How long did it take for the first galaxies to form? If we are seeing 13.7 billion light years away we are looking at galaxies. Did they form that quickly?
Assuming that's possible, how long would that thing be?
It's not about how long, really, it's about how wide. This is a fairly simple calculation to do using the Rayleigh criterion:
theta = 1.220 lambda/D
where theta is the angular resolution, lambda is the wavelength of light, and D is the diameter of the telescope we're using. Let's say we just want to resolve a planet with a diameter of 200000 km (bigger than jupiter, but not that much bigger) at a distance of say, 20 light years (there are roughly 60 stars with in this distance). The angular separation of such a planet is 20 km / 20 light years ~ 1 x 10^-9. If we look with 500 nm light, this means the diameter to actually resolve the planet (as opposed to a simple point of light) would be:
D = 1.220 * 500 nm / 1e-9 = 600 m
That's an awfully big optical telescope. The largest telescopes are typically 10 m; this would be 60 times bigger in diameter and 3600 times bigger in area. And that's just to barely resolve a giant planet in our local neighborhood of stars. In other words, it's not happening in the near future.
The inflationary phase of the Universe will eventually stop. Eventually all particles will decay and we will be back to a quantum state, where virtual particles pop in an out of existence. The total energy of our Universe is zero, everything we see and dont see is on borrowed time.
All particles eventually decay given time? Is photon particle? Does photon decay? Time means nothing to photon then how could it decay?
Another staple of science fiction faster than light travel is wormholes. Any comments from you, beninfla?
Quote:
Originally Posted by beninfl
Takes a lot of negative energy, and where would you put the wormholes exit?
Wormholes are break in fabric of space-time. Given that space-time is what we exist/rest on, how could you travel through wormholes without space-time. How do you even steer whatever the spaceship in the wormholes? What can you push/pull against in the wormholes to propel your spacecraft?
Are they thinking of wormholes as sinkholes and we travel through wormhole like some people falling into sinkhole? Do people forget that sinkhole is "powered" by gravity?
Last edited by kieplangdu; 07-26-2014 at 07:07 AM..
It's not about how long, really, it's about how wide. This is a fairly simple calculation to do using the Rayleigh criterion:
theta = 1.220 lambda/D
where theta is the angular resolution, lambda is the wavelength of light, and D is the diameter of the telescope we're using. Let's say we just want to resolve a planet with a diameter of 200000 km (bigger than jupiter, but not that much bigger) at a distance of say, 20 light years (there are roughly 60 stars with in this distance). The angular separation of such a planet is 20 km / 20 light years ~ 1 x 10^-9. If we look with 500 nm light, this means the diameter to actually resolve the planet (as opposed to a simple point of light) would be:
D = 1.220 * 500 nm / 1e-9 = 600 m
That's an awfully big optical telescope. The largest telescopes are typically 10 m; this would be 60 times bigger in diameter and 3600 times bigger in area. And that's just to barely resolve a giant planet in our local neighborhood of stars. In other words, it's not happening in the near future.
That's my whole point. I don't know the detail but the question can be easily answer using formula and solid number.
How long did it take for the first galaxies to form? If we are seeing 13.7 billion light years away we are looking at galaxies. Did they form that quickly?
Good question. First of all, we can only "see" optically ~8 billion light years, not using gravitational lensing. The only thing that comes close to 13.7 billion light years away was WMAP which occurs at a redshift z = 1089, or ~380,000 years after the Big Bang.
Optically, we can never see what happened before reionization. The cosmic Dark Ages were from ~380,000 years after the Big Bang, to ~400 million years after the Big Bang. It has been suggested that the first Population III stars appeared ~30 million years after the Big Bang. These would have been massive and very short lived stars.
As far back as we can see, using both radio and optical telescopes there has always been galaxies. The most distant galaxy that has been found is MACS0647-JD, which was ~13.3 billion light years away or ~420 million years after the Big Bang. However, take that with a grain of salt because they used gravitational lensing which can distort the light and make objects appear much further away than they really are.
If the distance is accurate, then galaxy MACS0647-JD would have had to form sometime between ~30 million years after the Big Bang and ~420 million years after the Big Bang. Probably much closer to ~420 million years than ~30 million years. So in the universal scale of things, the galaxies would have formed rather quickly. Galaxies probably formed within a few hundred million years after the Big Bang.
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