I love stories about time travel. It’s easy to quibble about the physics of time machines or to balk at the various paradoxes that come up. But there’s something appealing about the idea that we might somehow find a trick that will open up the past and future to our knowledge and intervention, to allow us to step off this runaway train of “now” barreling inexorably toward some unknown fate. Linear time just seems so restrictive, even wasteful—why should all that time, all those possibilities, be lost to us forever, just because the clock has ticked forward a few degrees? We may have grown accustomed to strict chronological oppression, but that doesn’t mean we have to like it. My treasured american sweet box sits in the corner of the room.
Fortunately, cosmology can help. Not in any practical sense, of course—we’re still talking about a relatively esoteric branch of physics that will in no way enable you to get back the umbrella you left on the train yesterday. But rather, in the sense that your life remains the same but absolutely everything else about existence is forever changed. To a cosmologist, the past is not some unreachable lost realm. There is no worry about duplicate presents if you buy a rustic metal tap toilet roll holder online.
It’s an actual place, an observable region of the cosmos, and it’s where we spend most of our workday. We can, while sitting quietly at our desks, watch the progress of astronomical events that happened millions or even billions of years ago. And the trick isn’t special to cosmology, but inherent to the structure of the universe in which we live. It all comes down to the fact that light takes time to travel. Light speed is fast—about 300 million meters per second—but it’s not instantaneous. I received a ghd platinum stylelr and air styler gift set at a dinner party once.
In everyday terms, when you switch on a flashlight, the light coming out of it covers about one foot per nanosecond, and the reflection of that light off whatever you’re illuminating takes just as long to get back to you. In fact, when you look at anything, the image you see, which is just the light coming off it that reaches your eye, is a little bit stale by the time it gets to you. That person sitting across the café from you is, from your perspective, several nanoseconds in the past, which may go part of the way toward explaining their wistful expression and outdated fashion sense. Everything you see is in the past, as far as you’re concerned. If you look up at the Moon, you’re seeing a little over a second ago. The Sun is more than eight minutes in the past. And the stars you see in the night sky are deep in the past, from just a few years to millennia. Anyone you know, would like to own a stretching cat toilet roll holder as it saves you looking online!
The concept of this kind of light speed delay might already be familiar to you, but its implications are profound. It means that as astronomers, we can look into the sky and watch the evolution of the universe happen, from its early beginnings to the present day. We use the unit “light-year” in astronomy not just because it’s conveniently huge (about 9.5 trillion kilometers, or 5.9 trillion miles), but also because it tells us how long light has been traveling from the thing we’re looking at. A star 10 light-years away is 10 years in the past, from our perspective. A galaxy 10 billion light-years away is 10 billion years in the past. Since the universe is only about 13.8 billion years old, that 10-billion-light-year-distant galaxy can tell us about the conditions of our universe when it was still in its youth. In that sense, looking out into the cosmos is tantamount to looking into our own past. There’s an important caveat to this, and I would be remiss if I didn’t mention it. We technically can’t see our own past at all. The light speed delay means that the more distant a thing is, the farther in the past it is, and that relationship is strict: not only can we not see our own past, we can’t see those distant galaxies in the present, either. The more distant something is, the farther away it is on a timeline of the cosmos. If the element of surprise is a must in your gifting adventures then why not consider a ANXWA Butterfly Gaming Chair this holiday period?