The Speed of Reflection

Would you be able to see yourself in a mirror if you were travelling at the speed of light? Explain why.

#SpecialRelativity

This discussion board is a place to discuss our Daily Challenges and the math and science related to those challenges. Explanations are more than just a solution — they should explain the steps and thinking strategies that you used to obtain the solution. Comments should further the discussion of math and science.

When posting on Brilliant:

Use the emojis to react to an explanation, whether you're congratulating a job well done , or just really confused .
Ask specific questions about the challenge or the steps in somebody's explanation. Well-posed questions can add a lot to the discussion, but posting "I don't understand!" doesn't help anyone.
Try to contribute something new to the discussion, whether it is an extension, generalization or other idea related to the challenge.
Stay on topic — we're all here to learn more about math and science, not to hear about your favorite get-rich-quick scheme or current world events.

Markdown	Appears as
`italics` or `_italics_`	italics
`bold` or `__bold__`	bold
- bulleted - list	bulleted list
1. numbered 2. list	numbered list
Note: you must add a full line of space before and after lists for them to show up correctly
paragraph 1 paragraph 2	paragraph 1 paragraph 2
`[example link](https://brilliant.org)`	example link
`> This is a quote`	This is a quote
# I indented these lines # 4 spaces, and now they show # up as a code block. print "hello world"	# I indented these lines # 4 spaces, and now they show # up as a code block. print "hello world"

Math	Appears as
Remember to wrap math in `$` ... `$` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$

Comments

NO Because light rays cannot reach before us as we are travelling at the speed of light. So there will be no reflecting back of light into our eyes. Hence we can't see ourself in the mirror if we were travelling at the speed of light.

Satyam Choudhary - 7 years, 2 months ago

No. Because light need to be faster than me to fall on the miror and reflect back to my eye but in this case the light will not reflect

mena george - 7 years, 2 months ago

Nope, and there is one experiment can prove it. You drive a car on a road. The light traffic is light, but you can't see the light beam, except in the special weather like frog and you just can see the light traffic if you look staight at the light traffic :D

Vladimir Tsiolkovsky - 7 years, 2 months ago

Light travels in such large quantities that it can be considered one mass (kind of). That's why you never have holes in your vision, because light is pretty much ALWAYS present, bouncing around all over the place. Anyways, if you move faster than the speed of light, three things will happen:

You will get larger You will expand. Remember $E=mc^{2}$ ? That says that nothing can travel the speed of light because then it will pick up mass and require more energy to move. That will be one thing happening to you.

You will warp It's part of the Theory of Relativity. Aside from the picking up mass, your physical being will be warped, stretched, but mass will not be gained. It's called length contraction.

Time will dilate Things going at fast speeds see everything else slower than they actually are. It's hard to say exactly how this would affect the experiment, but it would have some effect.

So when you zoom by the mirror, in theory, for you to see yourself, light must travel from the mirror to your eyes. Let $d$ be that distance. Let $l$ be your length. The light reflected by your stomach will have to travel $2d$ distance (for the light to travel there and back) in the same time that half of your body covers distance (assuming that your eyes are halfway between you back and front). Thus $2d \approx l/2$ . There are many more factors to consider, so I'll leave that to other members. Anyways, depending on how far away the mirror is, you may or may not be able to see yourself. That is my conclusion. :D

Finn Hulse - 7 years, 2 months ago

Wow, I would have to have at least a full school day to figure that out, and here it took you maybe a few minutes. Maybe even more because my World Studies teacher gets extremely mad when someone doesn't pay attention. She makes you humiliated and practically tells you that your stupid.

Robert Fritz - 7 years, 2 months ago

:D I would like to humiliate your World Studies teacher, then. A taste of her own medicine. ;)

Finn Hulse - 7 years, 2 months ago

@Finn Hulse – No need, it's been taken care of😄

Robert Fritz - 7 years, 2 months ago

Your mass will increase, but that does not mean that you will get larger. Getting larger, I assume, means an increase in volume, which clearly isn't true. Just nit-picking, I suppose :P

Daniel Liu - 7 years, 2 months ago

No, you're right. Sorry about that. Oops!

Finn Hulse - 7 years, 2 months ago

@Finn Hulse – time dilation doesn't start at the speed of light. Time literally stops at the speed of light and if you go faster you would find time reversing.

Sharky Kesa - 7 years, 2 months ago

@Sharky Kesa – Yeah, I know.

Finn Hulse - 7 years, 2 months ago

@Finn Hulse – I have thought of a way to travel through time. I call it the negative singularity.

Sharky Kesa - 7 years, 2 months ago

@Sharky Kesa – Cool! Also I don't know much about the topic, but if someone tried to reverse gravity, wouldn't you need to be able to harness a mass greater than that of the Earth. Are there other possible insane possibilities.

Robert Fritz - 7 years, 2 months ago

@Robert Fritz – No, it is the other way round. Since all objects with mass have gravity, and the higher the mass, the higher the gravity, 'anti-gravity' would require negative mass, which hasn't actually be observed but it has been theorised that black holes might convert particles into positive and negative mass, via Hawking Radiation this is hypothetical. Negative mass is the only one I know to reverse gravity although if gravity was polarised and you reversed the polarisation, it is possible to get 'anti-gravity'.

Sharky Kesa - 7 years, 2 months ago

@Sharky Kesa – Really? That's pretty cool! I thought that if a mass large enough to counter earths gravitational pull was able to be harnessed, then we could have anti gravity.

Robert Fritz - 7 years, 2 months ago

@Robert Fritz – That's not antigravity. That's just shifting gravity to another object. What you're saying is if, say, the moon became twice as large as Earth. Then everybody would fall towards the moon. That would suck, though, because it would be like falling on Earth from 384,000 kilometers above the surface. If what you're talking about is having an object with the exact same mass as earth, then theoretically, that would cause antigravity, but the construction presents many problems. Anyhow, it would be the same as if you were just floating around empty space. :D

Finn Hulse - 7 years, 2 months ago

@Finn Hulse – My thoughts exactly.

Sharky Kesa - 7 years, 2 months ago

@Sharky Kesa – :D

Finn Hulse - 7 years, 2 months ago

@Finn Hulse – Jeez. I just wanted to be able to fly.

Robert Fritz - 7 years, 2 months ago

noooo

akash dheer - 7 years, 2 months ago

Not at all

Harsh Shah - 7 years, 2 months ago

shashwat pandey - 7 years, 2 months ago

Math	Appears as
Remember to wrap math in `\(` ... `\)` or `\[` ... `\]` to ensure proper formatting.
`2 \times 3`	$2 \times 3$
`2^{34}`	$2^{34}$
`a_{i-1}`	$a_{i-1}$
`\frac{2}{3}`	$\frac{2}{3}$
`\sqrt{2}`	$\sqrt{2}$
`\sum_{i=1}^3`	$\sum_{i=1}^3$
`\sin \theta`	$\sin \theta$
`\boxed{123}`	$\boxed{123}$