“The question now is whether the majority of the very most massive galaxies form very early in the universe.” ~ Peter Capak
I love the above quote, taken from this Discovery News article, because of the way that it is worded. It sounds like Mr. Capak is speaking about something that supposedly happened a long time ago (and considering that the Universe is estimated to be around 13 billion years old, early on is a really long time ago indeed) in present tense. Why I like this is because, essentially, a lot of what we are looking at way out in space did happen a long time ago. This all has to do with the speed at which light travels.
Light is fast. In fact there isn’t suppose to be anything faster (though I remember reading something not too long ago about some experiment that aimed to show that something could theoretically travel faster than light, I cannot recall the exact details unfortunately). It travels at about 186,282.397 miles per second. But the Universe is a really big place and so even at the amazing speeds at which it is traveling light takes time to get from point A to point B. What this means is that a lot of the light that we see from stars in the night sky has taken quite awhile to reach Earth. We talk about light years, which is a measurement of the amount of distance light will travel in one year. Alpha Centuri, our closest neighboring star, is about 4.37 light years away from our solar system, meaning that if we were to travel at the speed of light it would take us about four and a third years to get there from here. Observing the red shift (an increase of wavelength of electromagnetic radiation) of distant stars and galaxies, showing us that they are moving away from us, and doing some math (probably some type of triangulation) scientists are able to estimate a general idea of how far away said light sources are and thus determine how long ago the light originated. In this way, the light that we receive from distant stars and galaxies is actually old because it has taken so long for that light to reach us (the light from Alpha Centuri is 4.37 years old). What this in turn means is that people like Mr. Capak can talk about an event that happened a long time ago in present tense because we are observing the light of the ancient occurrence in our present day.
This is awesome to me.
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