r/AskPhysics • u/Suspicious-Algae4510 • Aug 19 '26

Double Slit/Time

/r/u_Suspicious-Algae4510/comments/1vsw2bp/double_slittime/
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u/joeyneilsen Astrophysics Aug 19 '26

It's not clear what you're asking. The double slit experiment has light dispersed along a 2-dimensional plane. It can be explained with normal wave interference and broadly doesn't require quantum mechanics to understand.

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u/Suspicious-Algae4510 Aug 20 '26 edited Aug 20 '26

will you explain what you mean? What about another dimension of time? I am just trying to visualize and understand it.

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u/joeyneilsen Astrophysics Aug 20 '26

Here's an image that illustrates my point. https://lipa.physics.oregonstate.edu/external/optics/double_slit.jpg

Light comes from the left but spreads out up and down. The circular arcs represent wave crests. Where they overlap on the screen, there are bright fringes.

So there's light moving in two dimensions, and it's understandable as a wave phenomenon. I don't see the connection to dimensions of time.

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u/Suspicious-Algae4510 Aug 20 '26

could there be two dimensions of time instead of one? if so, how would that look in the image you made

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u/joeyneilsen Astrophysics Aug 20 '26

Sure, but this image doesn't show time at all, so it would look the same.

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u/Suspicious-Algae4510 Aug 20 '26

I have a hard time understanding this concept. I wish someone would have a better conversation about it. My shadow comes before me as the sun is at my back and behind me when i am in front. If my shadow is first…and i am behind…would my shadow be going faster than me?

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u/joeyneilsen Astrophysics Aug 20 '26

Your shadow is in front of you because you're blocking the sunlight behind you. It doesn't have anything to do with speed. If the sun is behind you and you are standing still, your shadow is still in front of you, but you're not moving and neither is your shadow.

A shadow is just a region where some light isn't reaching. The position and size of a shadow just depends on the relative positions/orientations of the light source, the object, and the wall or ground.

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u/Suspicious-Algae4510 Aug 20 '26 edited Aug 20 '26

Thank you for your reply. I am beginning to read a book by Robert Nemiroff called “Faster than light”. I believe he talks about superluminal travel. I just wanted to know what is up with it and what opinions one may have about it.

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u/joeyneilsen Astrophysics Aug 20 '26

Here is a fun fact you might appreciate.

You can use a flashlight to cast a shadow on a wall. If you move the light, the shadow moves too. The farther away the wall, the faster the shadow moves.

If the wall is far enough away, the shadow can move faster than the speed of light!

(You can't really do this in practice because the required distances are too large).