It is said that the Hubble Telescope can see farther into space than any telescope on earth. And that seeing deep into space is actually seeing the past, because the light hitting the telescope is not happening "now’ but is light that left whatever star however many years ago.
But my question is this, if the Hubble can see deeper than the most powerful telescope on earth, isn’t it really seeing the past AND the future (in a sense). Because the light it is seeing hasn’t hit earth yet (or the range of an earth boud telescope yet)…but presumably it would eventually hit earth when the light gets closer.
Am I way off or not understanding the concept right?
The time between when light from a distant object hits Hubble and when it hits the earth is a fraction of a second. Even if it is seeing things slightly before we on earth can, by the time the image is composed and sent on to earthbound scientists, the light already arrived at our earthbound scopes.
No matter how big the magnification and light gathering power of Hubble (and their are bigger instruments on earth) it only “sees” light that has arrived at the mirror.
Here, let me try to explain, assuming I understand the OP. Dicey I know.
Draw a horizontal line (-). Now somewhere along this line draw a vertical line (|). This vertical line is the location of the Earth in time. OK? The horizontal line is a physical location, the vertical line is time. Now draw a cone (/) at some point elsewhere on the horizontal line. Ideally make it a 45 degree angle to the horizontal. This is the path of a photon from some event located elsewhere in the universe. Notice where the diagonal line meets the vertical line? That’s when the light is “seeable” at our location. Notice that we see it at future time relative to when it first occurred (i.e. where the cone touches the horizontal line). We are seeing an event from the past.
You’re asking if you had two telescopes, one in orbit, and one on earth, would the one in orbit detect an event sooner than the one on earth - thereby making it the “future” in relation to the one on earth?
That would depend on where they are in relation to each other.
There could be events that a Plutonian (Plutorian? Plute?)could see that would be in our future. However there would be no way for the Plutonian to notify the Earthling (or vice versa) beforehand, so it’s of no value.
It takes less than 2 seconds for light to get from the moon which is 240,000 miles away. Hubble is a few hundred miles up. Don’t know exactly but less than 400.
With light traveling 186,000 miles per second how much difference is there going to be between an earth telescope and the Hubble. And with light coming from TEN BILLION light-years away what is a hundred thousandth of a second going to matter?
read TAU ZERO by Poul Anderson
to get an interesting perspective on the size of the universe and the speed of light.
Speaking purely semantically and for the purposes of formulating a fun riddle:
Hubble is “technically” seeing light before an earthbound scope (which is “the future”), but since that light hits the earth so fast, after it hits Hubble, the “the future” is undetectable and unreportable.
The example of someone looking through a telescope on Pluto is a good one. The guy on Pluto would see the light faster than the guy on earth (which is “the future”), and the light he sees is also “the past” because it isn’t happening now, it happened however many billions of light years ago.
FWIW…Gravitational lensing is one way to see the same event twice (depending on the positions of the object [i.e.-a supernova in an extremely distant galaxy] being lensed and the closer object [i.e.- another galaxy w/ a massive black hole] doing the lensing of the distant object), but you would not see the same exact set of photons twice…just a slightly different angle of the object that had a slightly longer trip to our mirror.
Not sure if you can call that “looking into the future”; more like “looking at re-runs” when the second event shows up.
Q: Can you see more than two events of the same thing with grav. lensing?
In principle, you can see the same event an infinite number of times depending on the details of the lens caustics and the paths of the light beams. However, two is the most common solution (just like a double image is the most common strongly lensed image).
Kinda depends the angle of the object being viewed/. Hubble is not very far from Earth… only about 350 miles. If it’s looking at something not directly away from Earth, some of the light from the object might hit parts of Earth closer to it than Hubble is.
Hm. Nobody seemed to understand the OP’s question back in 2004.
The answer, of course, is that Hubble sees further into the past because it can see dimmer objects than telesopes on Earth, it has nothing to do with seeing the light first.
Remember that since no one is on the Hubble, even though it might see something a fraction of a second earlier than when the info hits earth, no one on earth will know about it until the signal is transmitted here at the speed of light, which would arrive no more quickly than light from the object Hubble is studying. I’m ignoring processing and communication time for simplicity - we’d probably see it before the Hubble signal gets here in reality.
