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At the speed of light

Abstract depiction of light traveling

By C. Jimenez

The second topic in my blog: a teenager's journey through the mysteries of the cosmos.

The study of light, in physics, is called optics. Optics deals with the properties of light, how it interacts with other objects, and how it can be used. I find speed to be light's most intriguing property.

In 1676, Ole Christensen Rømer was the first to measure the speed of light using an astronomical measurement. Throughout the years, other scientists measured light's speed using various methods and now we have a standard measure of 299,792,458 m/s. This means that light can circle the Earth 7.5 times in just one second!

Given the vast distance between celestial bodies and Earth, light has been adopted as a point of reference for measuring distance in space. A light year is how far does light travel in one year. That is approximately 6 trillion miles, for perspective: it is 91.7 million miles from Earth to the Sun.

Two questions raise from here:

a) Can humans travel at the speed of light?

b) Is time travel possible?

Can humans travel at the speed of light?

The simple answer to that question is NO.

Light is fast because it is made out of mass-less particles called photons. All humans have a mass (which is different from weight). Following the theory of relativistic mass (image)

where c=speed of light, v=object's speed, and m0 is the initial object's mass), the observed mass (m) increases as speed increases. The speed of cars, trains, or airplanes have no significant impact on the mass, however when moving at [closer to] c, the observed mass approaches infinite. When m is infinite, then Einstein's E=mc2 says that E (energy) is also infinite. That is the energy required to keep the object moving at c. To this day, that is impossible though scientists continue looking for "loopholes" in the theory that could help us travel at nearly speed of light.

Imagine for a moment that it is possible, how could the vessel avoid crashing into debris when traveling at such speed?

Is time travel possible?

The answer to this question is complicated as it is still an unsolved equation. The scientific opinion appears to be that time-travel wouldn't be like seen in the movies where people are teleported to a different time. Furthermore, current theories suggest that traveling to the past is [nearly] impossible however traveling to the future is achievable.

While the speed of light doesn't really determine the answer to the question, I personally believe these two points of view:


1.- When we look into space, we are observing light that has been traveling in space for years, decades, millennia, and more. The images we receive from far away galaxies are showing us how things were hundreds even millions of years ago thus we are effectively observing past events.

JADES-GS-z13-0 is the farthest galaxy known, located 33 billion light-years away, estimated to have formed just a few hundred million years after the Big Bang. Studying this galaxy is like looking through a window into a past event that could explain our present without us having to physically "travel" to the past to see it. Isn't that cool ?

2.- On the other hand, travel to the future theoretically is possible by speeding up the passage of time as experienced by someone traveling in space. This phenomena is presented in the movie Interstellar. A person could sit for 1-2 hours at the edge of a black hole, where time travels slower relatively to Earth's just to realize upon landing on Earth, it's been already 1000 years! This person has effectively "traveled to the future", unfortunately cannot travel back.

In any case, scientist are still working hard to find a solution to this problem with a unified theory that connects special relativity with modern day quantum mechanics and I cannot wait to hear more as I immerse myself more in this field.

If you are interested in diving deeper into these topics, I recommend you check out “A Brief History of Time,” by Stephen Hawking. His book goes in depth about the topics of famous astronomers, relativity, dark matter, black holes, and a lot of astrophysics.

Let me know in the comments below what you think of this topic,

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