My question for today is: What does it mean to say time is the fourth dimension?
To truly understand I suspect you need symbols and equations, but if you relax your brain and don’t over think, you should get the general idea.
We live in three dimensional space. Objects make that clear. A box has width, depth and height (in my other life I’m a box maker).
But in order for the box to exist it must exist in a specific time. It exists now, or did in 1235, or will in 2317. Okay, but what does that mean?
Let’s say you want to meet a pal for lunch. You decide to go to the Skinny Pancake. You have decided on a place in space, a location. That location is defined by the space around us. For instance, the restaurant is located on the corner of State and Main. That gives a point where two lines (in this case streets) meet, the “X” which marks your spot, so to speak. If you lived in a large town you might need to invoke a third dimension – it’s on the first floor. You have now defined space by using three different reference points, that is; three dimensions.
“That’s all well and good,” your pal says. “But when shall we meet?” Ah ha! You need one more set of instructions to allow your plans to work. It turns out that Friday at 1:30 works for you both. A physicist would say you just added another dimension to your plans. You have now defined the time as well as the space for your lunch.
Space (as we know it) is three dimensional. The Skinny Pancake is located in space. But it also exists in time. You need that fourth dimension to fully describe your lunch date.
You can put an object in space, but time is needed to make it understandable, whether that time is a millisecond or a millennium. Without time existence is impossible. We take time for granted because we live in it. We don’t need to consciously think: my cat exists right now in this same time as I am existing.
Yet time is essential none the less. We can talk about now or the past or the future, but in each case it adds another description to the equation. That is why time can be thought of as a fourth dimension.
Enjoy your lunch.