Does the Bible teach that the Earth is round or flat?
The Christian faith recognizes the Bible above all other sources of knowledge as the inspired word of God. Teaching that contradicts the Bible is false, by definition. On the other hand, the Bible is not the sole source of knowledge in Creation.
For example, the Bible does not attempt to teach mathematics, chemistry, biology or many other areas of knowledge that are self-evidently true despite being absent in God's word. Therefore, we cannot become blind to obvious truths of nature, nor should we dismiss or ignore extra-biblical sources of truth so long as they do not contradict scripture.
In the case of the earth's shape, scripture never explicitly states the shape of our planet, nor does the Bible propose to teach the physical design of earth explicitly at any point, but it does confirm a round earth implicitly in various places. For example, the Creation account in Genesis 1 says that the earth began as water only, and water suspended in space always takes the form of a sphere due to the surface tensions of water molecules.
Furthermore, when dry land appeared, Genesis 1 describes all the land as existing "in one place" in Genesis 1:9 while all waters are gathered likewise. Geometrically, this can only happen on a sphere, and therefore Genesis 1 implies a round earth.
Nevertheless, the Bible is not our only (or even our best) source of information on the shape of the planet. Science long ago confirmed the spherical shape of the earth. As early as the 6th century B.C., men had mathematical proofs demonstrating the earth is spherical in shape. In the following centuries, many scientists have devised simple experiments validating the earth is a sphere, and more recently high-altitude aircraft, satellites orbiting our planet, and manned space travel have confirmed those earlier findings.
Even our own observations from the ground confirm the earth to be a sphere. When standing on the shore looking out on the horizon, the curvature of the earth cuts off the bottom of ships in the distance.
Simply put, men have known the earth was round for centuries, and the Bible confirms this truth implicitly. Unfortunately, some Christians have become victims of false teaching and conspiracy theories that misinterpret various scriptures to support bizarre conclusions. The claim of a “flat” earth is one such false teaching.
Moreover, we caution every Christian against becoming deceived by false teaching that opposes plains truths and promote novel and sensationalistic myths. Paul said such interests would be evidence of the end times, when believers are swept away by false teaching:
The popularity of “flat earth” teaching among a few deceived believers is indicative of the enemy's efforts to distract believers from Kingdom work with empty chatter and so-called "knowledge" which are actually sensationalistic myths. Paul says learning sound doctrine requires endurance, but some would prefer to have their ears tickled. The enemy uses attractive myths like a flat earth to distract believers from the truly important matters of scripture.
Therefore, we exhort believers to set aside these matters entirely. Do not waste time in endless and unprofitable arguments on one side or the other of these myths. Return to scripture seeking a meaningful understanding of Christ and your walk with Him that will profit you into eternity.