The Tipler cylinder is a cylinder of dense matter and infinite length. Historically, Dutch mathematician Willem Jacob van Stockum (1910–1944) found Tipler cylinder solutions to Einstein’s equations of general relativity in 1924. Hungarian mathematician/physicist Cornel Lanczos (1893–1974) found similar Tipler …

First, let’s define a time travel paradox. It is an occurrence that apparently violates some aspect of causality typically associated with time travel. Many science students are introduced to the oddities of the double slit experiment in an advanced high school science …

Internet searches for the keyword acronym “UFO” (unidentified flying object) are among the most popular on the Internet. According to Google, there are five million global searches per month for the keyword acronym “UFO” (without the quotes). Let us start …

The flow of time, sometimes referred to as the “arrow of time,” is a source of debate, especially among physicists. Most physicists argue that time can only move in one direction based on “causality” (i.e., the relationship between cause and …

Scientists have proposed using “wormholes” as a time machine. A wormhole is a theoretical entity in which space-time curvature connects two distant locations (or times). Although we do not have any concrete evidence that wormholes exist, we can infer their …

Today’s science knows precious little about negative energy. The best example we have of creating negative energy in the laboratory is the Casimir effect, which we briefly discussed previously, but will now discuss in detail. Let us start by discussing …

Without doubt, harnessing sufficient energy is  the largest obstacle to time travel. For example, time dilation (i.e., forward time travel) is only noticeable when mass approaches a significant fraction of the speed of light or sits in a strong gravitational …

Are there any real time machines? In my opinion, we are in about the same place space travel was at the beginning of the twentieth century. At the beginning of the twentieth century, all we knew about space travel came …

There are no existing time machines capable of sending humans forward or backward in time. The closest we have come to time travel is using particle accelerators to cause subatomic particles to experience time dilation (i.e., forward time travel). There …

Do time travel paradoxes spell doom to time travel? The short answer is no. Many in the scientific community do not think time travel paradoxes present an insurmountable barrier to time travel. Many physicists have suggested solutions to time travel …