is it true that a star in the sky isnt really there??

Question

my mate said that stars dont exist the light we see r from billions of years ago but the stars r not there ??? now she confused me at this point lol so r the stars really there????? simple terms if u please :))

well 2 pongo 306 of course im bothered or i wouldnt have lost 5 point asking the question ...duhhhh..

>>>pogo>>>>

Answer 1

you are looking at light today that was produced in a star a while ago. Not billions of years as your mate claims. I know some of you will have a problem with that statement. read on.

First, a light year is the distance light travels in a year. about 5 trillion miles. therefore the speed light travels from stars is 1 light year per year

Second, the closest star, other then our sun, to earth is about 4 light years away. which means light leaves that star, travels for 4 years then hits your eyeballs. The 25 closest stars are within about 10 light years of earth.

Earth is roughly in the center of the universe. The universe is about 45 billion light years in diameter (although this number is highly debated and the age of the universe is only believed to be 13 billion years.

Anyway you look at it, the farthest star you can possibly see would be 10's of billions of light years away. meaning the light you're looking at would have been produced 10's of billion of years ago. And those stars could be burned out. However, there are many many many more stars closer. Those are ones you see at night, they are closer and brighter. The ones farther away have had there light dispersed and washed out by billions of light years of universe, other light, and our atmosphere. As far as I can tell, the farthest "naked eye" observations are about 10 million light years (m81 is barely visible on rare occurances if you know what your looking for and it is 12 million light years away).


FYI, the sun is 93 million miles from the earth. speed of light is 186,000 miles / sec. so....


93,000,000 mi x (1 sec / 186,000 mi) = 500 seconds

500 seconds is a little over 8 minutes

that is, when you look at the sun, you looking at the way it was 8 minutes ago

Answer 2

Your mate's understanding of distances in space is incorrect. It is true that the light from the farthest galaxies was emitted 13.2 billion years ago. However, light from the nearest star was only emitted 4 years ago.

Our Sun is an average star. It has an expected life span of 10 billion years. Other stars may live longer or shorter. If we use this as a rule of thumb, then we would say that all stars within 5 billion light years are still alive since it would take 5 billion light years for light from the farthest ones to reach us and they would today be roughly in the middle of their lives.

Let's put this 5 billion light years into perspective. The diameter of the Milky Way is 100,000 light years across. This is WELL within the 5 billion figure meaning that virtually ALL starlight emitted from stars within our galaxy are still there. Let's go out farther- how about the entire Universe?

The visible universe is 13.7 billion light years in radius. This means that 1/3 of all the stars in the entire universe would be still alive today.

The only truth to your mate's statement would be that a galaxy let's say 10 billion light years away would have travelled another 10 billion light years away from us by the time it took it's light to reach us. Such galaxy would then be 20 billion light years away TODAY.

The naked human eye is able to see about 2000 stars in the sky away from city lights. Almost all of these lie between 10-100 light years away. Therefore, almost NONE of the stars visible to the naked eye could have gone out by the time their light reached us. Actually having a star supernova during your lifetime is a rare occurance.

Answer 3

What your friend says is partially right. The light from stars does take a long time to reach us but most of the stars we can see with the naked eye are much closer than "billions" of light years away. The nearest is only about 4 light years away.

As for it not being there, well that is possibly true.

The light from most of the stars we can see set out on its journey to us many years ago, in some cases thousands of years ago and in the case of radio and giant optical telescopes, millions or billions of years ago.

If a star ceased to exist as soon as the light left it we would not be aware of that fact until the light from the event itself reached us sometime in the future.

That is not to say that they are not there, only that they may not be there. There is a difference.

Answer 4

Its possible its not their anymore.
We measure the vast distances of space in light-years. (the distance light travels in a year.) This is because light is the fastest thing in the Universe.

Anyway if a star appears to be 1 billion light years away, the light from that star left that star 1 billion years ago, before life existed on Earth. If that star was towards the end of its life it could have died during that billion years. So yes that star might not exist anymore.
The light that it emitted just before it died is still travelling towards us so we wont know until maybe 900million years in the future.

The light from the sun takes about 8.5 minutes to reach Earth. So if the Sun were to explode we wouldnt know for 8.5 minutes.
Light is the fastest travelling thing in the universe and it takes time to travel the vast distances.

The speed of light (C) = 300 000km PER SECOND!!! Its the universe fundamental speed limit and nothing can go faster. Not quite sure why but as far as we know nothing can.

Answer 5

While light from a star billions of light years away shows you the star as it looked billions of years ago, but most stars are much closer than that. Sirius for example, is only 9 light years away and we see it as it looked 9 years ago.

His point is that if a star 10 billion light years away burned out less than 10 billion years ago, we could still see it even though it had already burned out. But no star farther away than a few thousand light years can even be seen without a telescope. And if Sirius burned out 10 billion years ago, it would have vanished from sight in our sky 9,999,999,991 years ago. The fact that we can still see it means it is still there as of 9 years ago. Since stars last many millions or even billions of years, you can be sure that all the naked eye stars in the night sky are really still there.

Answer 6

All you can say for sure is that the star was there when the light set out on its long journey to your retina. In some cases, this journey has taken billions of years, for nearer stars, only a few years, the nearest star other than the sun is about 4 light years away.

Our sun is about 6 light minutes away, so you are seeing the sun as it was 6 minutes ago. It could have vanished and you wouldn't know about it until 6 minutes had past.

The universe is just an illusion constructed by your brain anyway, so I wouldn't worry too much.

Answer 7

Stars are so far away that it takes light a long time to reach the Earth. Depends how far away the star is, of course, but in some cases you are looking at the star as it was in Queen Elizabeth 1's time. It may still be there or it may not. We won't know for another 500 years or so.

Answer 8

Stars evolve over great periods of time. The largest stars use up their fuel fastest and may explode as supernovas. Because it may take even billions of years for the light to reach us we are viewing very ancient history. The star may or may not still be there or in the exact location we see it. It would be like having a car drive by but not being able to see its headlights until next year (has it been in an accident in the meantime?).

Answer 9

Lets say you are in Paris on a clear sunny day, and you see the Eiffel Tower from a mile away. The speed of light is 186,000 miles per second. We all know that Distance / Speed = Time.

So 1 mile / 186,000 miles per seconds = 0.000005376 seconds. Basically, this is the amount of time it took light from the Eiffel Tower to reach your eyes, in other words you are looking at the Eiffel Tower as it was 0.000005376 seconds ago!

Now lets say you are looking at the star Alpha Centauri which is 4.7 light years from Earth. It is so far away that it takes 4.7 years for its light to reach Earth as opposed to the Eiffel Tower which only takes 0.000005376 seconds from a mile away.

If that star were to blow up right now at this moment for whatever reason. We would still see that star for another 4.7 years from today because the light that left the star just before it blew up will take 4.7 years to reach Earth. So until those last bits of light (photons) stops reaching us we would still think that the star is there.

A light year is the distance light travels in a year...

Answer 10

All the stars you can see with the naked eye are within a few thousand (not billion) light years, and most of them are within a few hundred light years or less. Most stars live for billions of years, so the chances that one of the ones you can see has died since its light left for Earth is remote. Also, stars don't just suddenly wink out; they take millions of years dying, and astronomers can see it coming. There are only a handful of naked-eye stars that are candidates for dying in the next few million years.