1. How Dennis Gabor's Hologram Idea Stores a 3D Picture on Flat Film
In 1947, a Hungarian scholar named Dennis Gabor had an idea while trying to improve the electron microscope, a tool for seeing tiny things. [3] He wondered if he could record the complete "shape" of light waves onto a film. If he could do that, he thought he could recreate the light later to make a picture that looked three-dimensional. [3]
However, this idea could not become reality until a new tool was invented. In 1960, the laser was created. A laser produces straight, uniform light. [3] Two years later, in 1962, a practical hologram using a laser was made. [8] Gabor received the Nobel Prize for this technology in 1971. [3]
2. Why a Black Hole's Disorder Depends on Its Surface Area, Not Its Volume
Now, let us look at something very strange in space. In the 1970s, scientists discovered that the "disorder" (entropy) of a black hole is not determined by its volume (the space inside it). Instead, it is determined by the area of its surface. [6]
This fact goes against our intuition. Usually, how much stuff fits in a box depends on the box's volume. But for a black hole, the amount of "information" inside is also linked to the area of its surface. [6]
3. Bekenstein's Discovery: Space Has a Limit on How Much Information It Can Hold
A scholar named Bekenstein used black holes to ask a question: "What happens if we try to force too much information into a small space?" [2] He considered that if you pack in too much, that space collapses and becomes a black hole. [2]
This means there is a maximum limit to the amount of information you can fit in a region. This limit depends on the size of the region and the energy inside it. This rule is called the "Bekenstein limit." [5] Since the information in a black hole is linked to its surface area, not its volume, a new idea was born: perhaps the amount of information you can pack is always determined by the area of the surrounding surface, not the volume inside. [6]
4. 't Hooft's Question: Could the Black Hole Rule Apply to the Whole Universe?
In 1993, a Dutch scholar named 't Hooft asked a big question: "What if this rule is not special to black holes, but applies to every place in the universe?" [1]
If this is true, then everything that happens inside a certain region must be "written" on the surface (the boundary) that surrounds that region. [1] This means 3D information is recorded on a 2D surface around it. This is somewhat like a hologram.
5. Susskind's Idea: Is the World Made of Holograms?
An American scholar named Susskind pushed this idea further. He developed it within "string theory," a different theory that tries to explain everything using tiny, string-like things. [1]
In 1995, Susskind published a paper titled "The World as a Hologram." [1] The idea is that the visible 3D world, including stars, planets, and ourselves, might actually be a "projection" of information written on a 2D surface.
6. Maldacena's Math Example of the Holographic Principle, Explained With Canned Soup
In 1997, an Argentine scholar named Maldacena proposed a specific example where this holographic principle seems to work, using mathematics. [7]
This story is often compared to "canned soup" to explain the model. Imagine the soup inside the can (events in a volume). The information about that soup could be fully explained by the label on the outside of the can (writing on an area). [4] In a special model of the universe, this strange relationship is thought to be true, and research continues to check it. [4] However, we do not yet know if this applies directly to our own universe.
7. Try It Yourself: Compare Area and Volume With Building Blocks
You can check the difference between area and volume yourself. Use building blocks to make a cube, then double the length of each side. Count to verify that the area becomes 4 times bigger, while the volume becomes 8 times bigger.
If you have a hologram card or sticker at home, look at it from different angles. Observe how the picture changes depending on your view.
When you are curious, write down one word to look up later. For example, asking "Is the Einstein-Rosen bridge related to wormholes?" is a good start.